Automatic sphere grinder with automatic feeder

ABSTRACT

Lapidary apparatus for grinding rocks or stones into polished spheres, which are attractive works of art, comprising an automatic sphere grinder with automatic feeder, said apparatus including a grinding cup rotatable about a vertical axis and adapted to receive a work object to be ground into a sphere, a travelling boom, a pair of legs mounted on the boom and adapted to contact and rotate the work object, the legs contacting the work object on each side of the vertical axis of the cup to hold the work object in the cup, a motor crank arm connected to one end of the boom for reciprocably moving the boom and legs in a direction generally along the longitudinal axis of the boom so as to move the length of the legs over the work object to rotate it about a horizontal axis, a lift member mounted on the other end of the boom adapted to contact a stop member to momentarily lift the legs from the work object to allow the cup to spin the work object to another grinding position, a grit hopper having a feed port, a grit receiving member having an arcuate surface positioned below the feed port a distance such that when in normal position the arcuate surface receives a pile of grit having a positive angle of repose that shuts off the feed port, a shaft rotatably supporting the grit receiving member and having a handle extending downwardly therefrom of sufficient length to be heavy enough to support the arcuate surface in position beneath the feed port, a funnel mounted beneath the grit receiving member and over the work object, an actuating arm mounted on the boom and positioned so as to strike the handle to move the arcuate surface back and forth beneath the feed port to receive and dispense grit material into said funnel, and a water system with a water feed port positioned over the work object for feeding water thereto, the water feed port being positioned away from the funnel tube to prevent water from entering the funnel and clogging it with wet grit.

[ June 19, 1973 AUTOMATIC SPHERE GRINDER WITH AUTOMATIC FEEDER [76] Inventor: Joseph C. Sharbaugh, 164 Warrior Road, Drexel Hill, Pa. 19026 [22] Filed: May 17, 1971 [21] Appl. No.: 143,799

[52] US. Cl 51/105 R, 51/289 S, 51/317 [51] Int. Cl 1324b 11/10 [58] Field of Search 51/26, 73 R, 103 R,

[56] References Cited UNITED STATES PATENTS 3,133,383 5/1964 Chapman 51/289 S X 2,998,676 9/1961 Hawkins 51/289 S X 2,703,470 3/1955 Porter 51/289 S 1,988,649 l/1935 Evans 51/289 S UX 418,350 12/1889 Conrader 5l/289 S UX Primary ExaminerDonald G. Kelly Attorney-Smith, Harding, Earley & Follmer 57 ABSTRACT Lapidary apparatus for grinding rocks or stones intotact and rotate the work object, the legs contacting the work object on each side of the vertical axis of the cup to hold the work object in the cup, a motor crank arm connected to one end of the boom for reciprocably moving the boom and legs in a direction generally along the longitudinal axis of the boom so as to move the length of the legs over the work object to rotate it about a horizontal axis, a lift member mounted on the other end of the boom adapted to contact a stop member to momentarily lift the legs from the work object to allow the cup to spin the work object to another grinding position, a grit hopper having a feed port, a grit receiving member having an arcuate surface positioned below the feed port a distance such that when in normal position the arcuate surface receives a pile of grit having a positive angle of repose that shuts off the feed port, a shaft rotatably supporting the grit receiving member and having a handle extending downwardly therefrom of sufficient length to be heavy enough to support the arcuate surface in position beneath the feed port, a funnel mounted beneath the grit receiving member and over the workobject, an actuating arm mounted on the boom and positioned so as to strike the handle to move the arcuate surface back and forth beneath the feed port to receive and dispense grit material into said funnel, and a water system with a water feed port positioned over the work object for feeding water thereto, the water feed port being positioned away from the funnel tube to prevent water from entering the funnel and clogging it with wet grit.

7 Claims, 9 Drawing Figures PAIENIEB LM! 9 I75 mn'nrz I03 WATER IOI INVENTOR JOSEPH C.SHARBAUGH FIG.8.

ATTORNEYS PAIENIED 3.739.531

sum 2 or a JII 79 87 mvsu'ron i JOSEPH C. SHARBAUGH BY as M 39 FIG. 6. 75

ATTOR NEYS AUTOMATIC SPHERE GRINDER WITH AUTOMATIC FEEDER BACKGROUND OF THE INVENTION This invention relates to lapidary equipment and more particularly concerns a sphere grinder and automatic grit feeder for grinding rocks or stones into polished spheres which are recognized as attractive objects of art.

Lapidaries are people who cut, polish and engrave precious stones or rocks. Lapidaries may do this as a profession, or they may do this as a hobby and may join a lapidary society whose members enjoy working on stones and rocks.

It is believed that many more amateur lapidaries would be grinding rocks and stones into spheres if they did not think that sphere cutting was too difficult, too time consuming, and involved expensive equipment.

The simplest sphere grinder is a rotating cup. Loose grit is applied to the cup and a rock is held in the cup by hand and slowly rotated so that the grit grinds the rock surface into a sphere. However, grinding a sphere by hand involves constant attention and a great deal of time since it calls for rotating the rock by hand against the spinning cup and feeding grit and water to the cup with a paint brush as needed. Such a hand operation may take to 25 hours, or more, before the rock is ground into an acceptable sphere.

For a full description of the operation in hand grinding a sphere, I refer to my article entitled Sphere Grinding In The Bargain Basement which appeared in the TUSCARORA BULLETIN, a publication of the Tuscarora Lapidary Society, Inc., in the November and December, 1969 issues, such article being hereby incorporated by reference.

Instead of grinding rock or stone into a sphere by this hand method, a lapidary may use a machine. However, conventional machines may cost $100.00 to about $400.00. Also, such machines are fairly complicated and may include a pair of facing cutter cups and shafts. Such sphere maker machines are made by Covington Engineering Corp., Redlands, California, and by Highland Park Mfg. Co., Inc., S. Pasadena, California, for example.

SUMMARY OF THE INVENTION It is an object of this invention to provide an automatic sphere grinder including an automatic feeder, which apparatus is relatively simple and inexpensive.

The apparatus includes a rotatable grinding cup adapted to receive a work object such as a stone or rock to be ground into a sphere, a travelling boom, a pair of legs mounted on the boom for contacting and rotating the work object, a motorized crank arm for'reciprocably moving the boom and contact legs in a direction generally along the longitudinal axis of the boom, a stop member for contacting the end of the boom and lifting the legs away from the work object to allow the rotating cup to spin the work object to another position, and automatic feeder means for feeding a grinding material to the work object, said feeding means including a grit hopper having a grit feed port at the bottom for gravity feed therethrough, a grit receivangle of repose of the grit, a handle extending downwardly from said receiving element shaft and being heavier than the grit receiving element to maintain the receiving element in upright normal position, and an actuating arm mounted on the boom and adapted to contact said handle during reciprocation of said boom to rotate said receiving element shaft to move the receiving element and dump the grit from its top surface onto the work object.

BRIEF DESCRIPTION OF TIE-IE DRAWINGS Objects and advantages of this invention, including its simplicity and economy, as well as the ease with which it may be adapted for use with existing equipment, will become apparent hereinafter and in the drawings, in which:

FIG. 1 is a view in side elevation of an automatic sphere grinder with automatic feeder constructed in accordance with this invention, with parts being shown in section in order to better illustrate the invention;

FIG. 2 is a view in top plan taken as indicated by the lines and arrows 2-2 which appear in FIG. 1;

FIG. 3 is a partial view in side elevation, similar to' FIG. 1, but showing a later stage in operation with its lift lever resting on a stop member so as to release its legs from contact with the work object;

FIG. 4 is a view in section taken as indicated by the lines and arrows 4-4 which appear in FIG. 2;

FIG. 5 is a view similar to FIG. 4 but shows the stage of operation of FIG. 3 whereas FIG. 4 shows the stage of operation of FIG. 1;

FIG. 6 is an enlarged view of a portion of the automatic grit feeder showing how the grit forms a conical pile, because of the angle of repose of the grit, to shut off the grit feed port;

FIG. 7 is a view of a rough rock or stone which is to be ground into a sphere;

FIG. 8 is a view of the rock after it has been sawed into a more or less cube shape with the corners sawed off; and

FIG. 9 shows the rock in its final form after being ground and polished into a sphere by the apparatus of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Although specific terms are used in the following description for clarity, these terms are intended to refer only to the structure shown in the drawings and are not intended to define or limit the scope of the invention.

Turning now to the specific embodiment of the invention selected for illustration in the drawings, there is shown lapidary apparatus for grinding rocks or stones into polished spheres comprising an automatic sphere grinder 11 which includes an automatic grit feeder 13. Sphere grinder 11 includes a rotatable grinding cup 15 which is mounted on a vertical shaft 17 supported on table top 19 by support member 21. Shaft 17 is driven by pulley 23, belt 25, and pulley 27 on drive shaft 29 of cup motor 31 mounted on the bottom of table top 19.

Grinding cup 15 is adapted to receive a rock or work object 33 to be ground into a sphere.

A travelling boom 35 includes a central member 37 attached at one end to two side members 39, and a lift tive to sidemembers 39. Lift lever 41 is adapted to contact a stop member 45 mounted on table top 19.

A motor 47 is supported on table top 19 by bracket 49. Motor crank arm 51 is positioned in a hole 53 in the end of central member 37 of boom 35 so as to reciprocate boom 35 in a direction substantially along the axis of the boom.

Extending outwardly from side members 39 are square mounting blocks 55 which support circular mounting blocks 57 that contact legs 59 having ends inserted in radial holes in blocks 57. Legs 59 are provided with rubber tubes 61 for better contact with the surface of work object 33. Bolts and wing nuts 63 connect blocks 55, 57 together, and the legs 59 may be repositioned easily to accommodate different size rocks by turning back on wing nuts 63 to release the legs from mounting blocks 57, rotating blocks 57, and retightening wing nuts 63.

Splash pan 65 is mounted on table top 19 around spinning cup in order to catch any splashing of the grinding mixture being used to grind work object 33. A drain pipe 67 extends downwardly from splash pan 65 through table top 19.

Automatic grit feeder 13 includes a grit hopper 71 mounted above work object 33 hy horizontal support member 73 bracketed to slotted vertical support arm 74 which is connected to vertical support member 75 by bolt and wing nut 76, with the bolt passing through a vertical slot in support arm 74. Grit hopper 71 has a grit feed port 77 at its bottom for gravity feed of the grit therethrough.

A grit receiving element79 is positioned beneath grit feed port 77 for receiving a pile 81 of grit which closes feed port 77 because of the angle of repose of the grit. The pile 81 of grit forms a cone shape with the apex of the cone at the grit feed port 77 and the sides of the cone sloping downwardly and outwardly therefrom.

Grit receiving element 79, in the preferred form of the invention, is made of wood and has the shape of a pie segment which is mounted on a shaft 83 extending through a grit funnel 85 suspended from horizontal support member 73 by straps 87. Grit receiving element 79 has an arcuate top surface for receiving the grit, and shaft 83 has a handle 89 extending downwardly therefrom which is of sufficient length so as to be heavy enough to support grit receiving element 79 in normal upright position beneath feed port 77.

Grit receiving element 79 is actuated to dump pile 81 of grit onto work object 33 by an actuating arm 91 mounted on boom 35. Arm 91 contacts handle 89 during reciprocation of the boom to thereby rotate receiving element 79 about shaft 83 to dump the grit.

Funnel 85 is positioned around and beneath grit receiving element 79 and includes a cone-shaped body 93 with a tube 95 extending downwardly from the cone apex and terminating in a funnel feed port 97 above work object 33 and cup 15.

Automatic grit feeder 13 also includes a water reservoir 99 positioned above funnel feed port 97, and a gravity feed water tube 101 extending from water reservoir 99 to a position adjacent to but spaced away from funnel feed port 97 so that the water contacts the dumped grit after it passes through the funnel feed port 97, thereby preventing water entering funnel feed port 97 and clogging the funnel tube 95 with wet grit. Water tube 101 is provided with a valve 103 in order to regulate the flow of water.

In grinding a stone into a sphere by hand, the lapidary holds the stone in his hand and moves it against the edge of a rotating cup, adding a gritty paste made of carborundum or silicon carbide and water between the edges of the rotating cup and the stone. This work takes hours to cut a stone into a sphere.

In operation of the present invention, the stone or work object 33 is placed in spinning cup 15 and is rotated about a horizontal axis by legs 59 of boom 35 which, in the preferred embodiment of the invention, has a nine inch stroke imparted to it by crank arm 51 of motor 47. When crank arm 51 reaches the horizontal position illustrated in FIG. 3, lift lever 41 on boom 35 contacts stop member 45 which prevents further downward movement of lift lever 41 and lifts legs 59 away from the top of work object 33, thereby allowing cup 15 to spin stone 33 to another position. As crank arm 51 continues in its travel, legs 59 return into contact position on top of the newly positioned work object 33 and rotate the work object around a horizontal axis, thus moving the surface of work object 33 into contact with the edges of spinning cup 15 and the abrasive grit which grinds the surface of the stone. In operation of automatic grit feeder 13, the grit in hopper 71 pours through feed port 77 to form a pile 81 on the upper surface of grit receiving element 79. The pile 81 is in the form of a cone in accordance with the angle of repose of the grit, and when the pile grows big enough the cone of grit jams the exit port 77 to prevent more grit from passing therethrough. Accordingly, feed port 77 deposits a limited amount of grit on the top surface of grit receiving element 79 which rotates with shaft 83 when handle 89 is actuated by actuating arm 91 of boom 35. As grit receiving element 79 moves, the grit pours through feed port 77 to pour a continuous band of grit on the upper surface of receiving element 79, and the grit is dumped off this upper surface as element 79 is moved in a reciprocable motion.

One of the advantages of the automatic grit feeder 13 is that it feeds abrasive material and yet the abrasive material does not wear out the parts of the grit feeder because there are so few moving parts. In other words, there is no wearing surface in contact with the abrasive material.

It has been found that 400 grit fine silica does not work in automatic grit feeder 13 because it has a negative angle of repose and does not pour through grit feed port 77 which has a l/32 inch diameter. However, 200 grit silica and coarser grits work fine in automatic grit feeder 13.

Legs 59 are easily removable from mounting blocks 57 by turning back on the wing nuts 63 and should be removed to clean the coarse grit therefrom before going on to a finer grit. Also, rubber tubes 61 should be replaced so that each size grit has its own rubber tubes, thereby avoiding grit of different sizes being imbedded in the rubber and interfering with the progressive fine grinding of the work object.

Legs 59 may be opened and closed to fit the size of the work object 33 by rotating the position of mounting blocks 57 before clamping them in place by turning down on wing nuts 63.

Also, grit feeder support arm 73 is movable vertically because it is fastened to a vertical arm 74 that is vertically slotted and may be raised and lowered and then clamped in place by bolt and wing nut 76.

I claim:

1. An automatic sphere grinder comprising a grinding cup rotatable about a vertical axis and adapted to receive a work object to be ground into a sphere, means for rotating said grinding cup, a travelling boom, contact means mounted on said boom for contacting and rotating the work object, means for reciprocably moving the boom and contact means in a direction generally along the longitudinal axis of the boom, and means for lifting said contact means away from the work object to allow said cup to spin the work object to another position.

2. The automatic sphere grinder of claim 1 wherein said contact means comprises a pair of legs adapted to contact the work object with one leg positioned on each side of the vertical axis of the cup.

3. The automatic sphere grinder of claim 2 wherein said legs are covered with rubber tubing for better traction with the work object.

4. The automatic sphere grinder of claim 1 wherein said lifting means comprises a stop member adapted to contact the boom.

5. The automatic sphere grinder of claim 1 including means for feeding a grinding material to the work object, said feeding means for the grinding material comprising a grit hopper having a grit feed port at the bottom for gravity feed therethrough, grit receiving means positioned beneath said feed port for receiving a pile of said grit and closing the feed port because of the angle of repose of said grit, and means mounted on said boom for actuating said grit receiving means to dump said pile of grit onto said work object.

6. The automatic sphere grind-er of claim 5 wherein is also provided means for feeding water to the work object to mix with the grit.

7. The automatic sphere grinder of claim 5 wherein said grit receiving means comprises a grit receiving element mounted on a shaft and having a top surface positioned beneath said grit feed port for receiving the grit, a handle extending downwardly from said shaft, said handle being heavier than said grit receiving element to maintain the receiving element in upright normal position, and said actuating means comprises an actuating arm mounted on said boom and adapted to contact said handle during reciprocation of said boom to rotate said receiving element shaft to move the receiving element and dump the grit from its top surface. 

1. An automatic sphere grinder comprising a grinding cup rotatable about a vertical axis and adapted to receive a work object to be ground into a sphere, means for rotating said grinding cup, a travelling boom, contact means mounted on said boom for contacting and rotating tHe work object, means for reciprocably moving the boom and contact means in a direction generally along the longitudinal axis of the boom, and means for lifting said contact means away from the work object to allow said cup to spin the work object to another position.
 2. The automatic sphere grinder of claim 1 wherein said contact means comprises a pair of legs adapted to contact the work object with one leg positioned on each side of the vertical axis of the cup.
 3. The automatic sphere grinder of claim 2 wherein said legs are covered with rubber tubing for better traction with the work object.
 4. The automatic sphere grinder of claim 1 wherein said lifting means comprises a stop member adapted to contact the boom.
 5. The automatic sphere grinder of claim 1 including means for feeding a grinding material to the work object, said feeding means for the grinding material comprising a grit hopper having a grit feed port at the bottom for gravity feed therethrough, grit receiving means positioned beneath said feed port for receiving a pile of said grit and closing the feed port because of the angle of repose of said grit, and means mounted on said boom for actuating said grit receiving means to dump said pile of grit onto said work object.
 6. The automatic sphere grinder of claim 5 wherein is also provided means for feeding water to the work object to mix with the grit.
 7. The automatic sphere grinder of claim 5 wherein said grit receiving means comprises a grit receiving element mounted on a shaft and having a top surface positioned beneath said grit feed port for receiving the grit, a handle extending downwardly from said shaft, said handle being heavier than said grit receiving element to maintain the receiving element in upright normal position, and said actuating means comprises an actuating arm mounted on said boom and adapted to contact said handle during reciprocation of said boom to rotate said receiving element shaft to move the receiving element and dump the grit from its top surface. 